1. Field of the Invention
The present invention relates to a post cure inflator for expansion-cooling a vulcanized tire and a vulcanized tire cooling method.
2. Description of the Related Art
Generally, organic fibers of polyester, nylon or like material are used as carcass members as reinforcing fibers inside a tire. In the process of cooling a tire after completing the vulcanization, these reinforcing fibers are contracted. However, the degree of contraction is not uniform due to disparities, arrangement, molded state and the like of the members. In the natural cooling by merely leaving the tire, the tire is deformed due to differences in the degree of contraction, which makes the tire a defective product or deteriorates the uniformity performance of the tire.
Accordingly, air is normally filled into the inside of the tire by a post cure inflator after the vulcanization is completed, and the tire is cooled up to a certain temperature or lower (normally 100° C. or lower, desirably 80° C. or lower) at which the contraction of the reinforcing fibers stops while holding the tire in a proper shape (see, for example, Japanese Unexamined Patent Publication No. H06-143298, hereinafter, referred to as “Prior Art 1”).
A post cure inflator of the so-called two-point type having two upper and lower positions for cooling a tire and moving the tire between two handling positions by holding the tire and reversing it has been proposed and put to practical use as a post cure inflator of this type (see, for example, Japanese Unexamined Patent Publication No. H11-320564, hereinafter, referred to as “Prior Art 2”).
In recent years, it has been required to shorten the tire cooling time in order to cope with a shortened vulcanization time, and post cure inflators having various constructions for shortening the tire cooling time have been proposed and put to practical use. For example, Japanese Unexamined Patent Publication No. 2002-307444 (hereinafter, referred to as “Prior Art 3”) proposes a post cure inflator in which a hollow passage is formed in a rim mechanism for holding a bead portion of a tire, cooling air is supplied into and caused to flow along this hollow passage, and air or atomized water is sprayed on the outer surface of the tire, thereby forcibly cooling the tire to complete the cooling within a short period of time.
However, in the case of the post cure inflator of Prior Art 1, there is a problem of requiring a loner time to cool the vulcanized tire. Further, temperature at an upper part of the vulcanized tire tends to be higher by being influenced, for example, by a natural convection, one surface of the vulcanized tire facing a vulcanizer tends to be higher due to an asymmetric temperature environment around the facility, and the peripheral temperatures of the tires vary due to the asymmetric specification such as the pattern, construction and the material of the tires. Thus, the vulcanized tire cannot be cooled in a well-balanced manner along vertical directional and circumferential direction. The temperature difference caused by the cooling variation causes a problem of varying qualities such as conicity.
In the case of the post cure inflator of Prior Art 2, it is difficult to uniformly cool the entire outer surface of the tire, causing temperature irregularity and cooling irregularity along circumferential direction outside the tire. There are other problems of a complicated mechanism, a high equipment cost, and high maintenance frequency and cost.
In the post cure inflator for forcibly cooling the tire using the cooling medium such as cooling air or atomized water as disclosed in Prior Art 3, stains such as water marks are likely to attach at positions where the cooling medium such as water is sprayed, thereby causing a problem in the appearance of the outer surface of the tire. Further, since a mechanism including a driving source and a pipe for supplying the cooling medium needs to be installed around the apparatus, the apparatus is enlarged and the mechanism becomes complicated by these peripheral equipments and the parts cost is increased by installing the peripheral equipments. There is an additional problem of a considerable increase in the running cost by the operation of the driving source.